diff --git a/mathentry.py b/mathentry.py
index 8119ac3..f23c7d5 100644
--- a/mathentry.py
+++ b/mathentry.py
@@ -24,14 +24,20 @@ class MathEntry(wx.TextCtrl):
 
     def GetValue(self):
         val = super().GetValue()
+
+        if val == "None": #TODO?
+            return None
+
         try:
             val = self.value_type(val)
-        except ValueError:
-            pass
+        except (ValueError, TypeError) as e:
+            print(e)
+
         return val
 
 
     def SetValue(self, val):
+        self.value_type = type(val)
         val = str(val)
         super().SetValue(val)